U.S. patent number 4,536,998 [Application Number 06/594,927] was granted by the patent office on 1985-08-27 for flexible selective energy control sheet and assembly using the same.
This patent grant is currently assigned to Optical Coating Laboratory, Inc.. Invention is credited to Robert E. Hahn, John S. Matteucci, James K. Snyder.
United States Patent |
4,536,998 |
Matteucci , et al. |
August 27, 1985 |
Flexible selective energy control sheet and assembly using the
same
Abstract
Flexible selective energy control sheet construction formed of a
sheet of substantially transparent polymer thin film plastic
material having first and second surfaces. A substantially
transparent continuous adhesion promoting layer is adherent to the
second surface of the sheet. A substantially transparent metal
layer is adherent to the adhesion promoting layer and a protective
layer is adherent to the metal layer. The metal layer is selected
from the materials of copper and silver.
Inventors: |
Matteucci; John S. (Healdsburg,
CA), Snyder; James K. (Santa Rosa, CA), Hahn; Robert
E. (Santa Rosa, CA) |
Assignee: |
Optical Coating Laboratory,
Inc. (Santa Rosa, CA)
|
Family
ID: |
26976058 |
Appl.
No.: |
06/594,927 |
Filed: |
March 29, 1984 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
|
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308025 |
Oct 2, 1981 |
4463047 |
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Current U.S.
Class: |
52/171.3; 52/202;
428/216 |
Current CPC
Class: |
E06B
7/28 (20130101); E06B 9/24 (20130101); F24S
50/80 (20180501); Y02E 10/40 (20130101); Y10T
428/24975 (20150115); Y02B 10/20 (20130101) |
Current International
Class: |
F24J
2/40 (20060101); E06B 7/00 (20060101); E06B
7/28 (20060101); E06B 9/24 (20060101); E06B
007/12 () |
Field of
Search: |
;52/171,789,202
;428/666,626,926,458,457,658,668,333,671,674,432 ;350/1.7 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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2461716 |
|
Dec 1974 |
|
DE |
|
2703688 |
|
Aug 1978 |
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DE |
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1013630 |
|
Dec 1965 |
|
GB |
|
Primary Examiner: Murtagh; John E.
Assistant Examiner: Ford; Kathryn L.
Attorney, Agent or Firm: Flehr, Hohbach, Test, Albritton
& Herbert
Parent Case Text
This is a division, of application Ser. No. 308,025 filed on Oct.
2, 1981 now U.S. Pat. No. 4,463,047.
Claims
What is claimed is:
1. In an assembly of the character described, a frame, a pane of
glass mounted in the frame and having inside and outside surfaces
and an energy control sheet carried by the inside surface of the
pane of glass, said energy control sheet comprising a sheet of
substantially transparent flexible polymer thin film plastic
material having first and second surfaces, an optically active
substantially transparent adhesion promoting layer adherent to said
second surface of said sheet, said adhesion promoting layer being
substantially continuous, a substantially transparent metal layer
adherent to said adhesion promoting layer and a protective layer
adherent to said metal layer, said metal layer being formed of
silver and having a thickness ranging from 60 to 200 Angstroms,
said adhesion promoting layer and said protective layer being
formed of zinc sulphide and having a thickness ranging from 300 to
500 Angstroms.
2. An assembly as in claim 1 wherein said sheet of transparent
flexible polymer plastic material has a thickness ranging from 12
micrometers to 200 micrometers.
3. An assembly as in claim 1 together with a top coat carried by
said protective layer.
4. In an assembly of the character described, a frame, a plane of
glass mounted in the frame and having inside and outside surfaces,
an energy control sheet carried by the inside surface of the pane
of glass, said energy control sheet comprising a sheet of
substantially transparent flexible polymer thin film plastic
material having first and second surfaces, an optically active
substantially transparent adhesion promoting layer adherent to said
second surface of said sheet, said adhesion promoting layer being
substantially continuous, a substantially transparent metal layer
adherent to said adhesion promoting layer and a protective layer
adherent to said metal layer, said metal layer being formed of
copper having a thickness ranging from 100 to 500 Angstroms, said
adhesion promoting layer and said protective layer being formed of
chromium and having a thickness ranging from 10 to 200
Angstroms.
5. An assembly as in claim 4 wherein sheet of transparent flexible
polymer plastic material has a thickness ranging from 12 to 200
micrometers.
6. An assembly as in claim 4 together with a top coat carried by
said protective layer.
7. An assembly as in claim 6 wherein said top coat is comprised of
a film having a thickness ranging from 5 to 50 microns.
8. In an assembly of the character described, a frame, first and
second panes of glass carried by the frame and having a space
therebetween and a selective energy control sheet disposed between
the panes of glass, the selective energy control sheet comprising a
sheet of substantially transparent flexible polymer thin film
plastic material having first and second surfaces, an optically
active substantially transparent adhesion promoting layer adherent
to said second surface of said sheet, said adhesion promoting layer
being substantially continuous, a substantially transparent metal
layer adherent to said adhesion promoting layer and a protective
layer adherent to said metal layer, said metal layer being formed
of silver and having a thickness ranging from 60 to 200 Angstroms,
said adhesion promoting layer and said protective layer being
formed of zinc sulphide and having a thickness ranging from 300 to
500 Angstroms.
9. In an assembly of the character described, a frame, first and
second panes of glass carried by the frame and having a space
therebetween and a selective energy control sheet disposed between
the panes of glass, the selective energy control sheet comprising a
sheet of substantially transparent flexible polymer thin film
plastic material having first and second surfaces, an optically
active substantially transparent adhesion promoting layer adherent
to said second surface of said sheet, said adhesion promoting layer
being substantially continuous, a substantially transparent metal
layer adherent to said adhesion promoting layer and a protective
layer adherent to said metal layer, said metal layer being formed
of copper having a thickness ranging from 100 to 500 Angstroms,
said adhesion promoting layer and said protective layer being
formed of chromium and having a thickness ranging from 10 to 200
Angstroms.
10. An assembly as in claims 8 or 9 in which the energy control
sheet is adherent to a surface of said second pane of glass facing
said space.
11. An assembly as in claim 8 or 9 in which the energy control
sheet is disposed in said space between said panes of glass.
Description
This invention relates to flexible energy control sheets and
assembly using the same and more particularly to such sheets and
assemblies thereof in which improved visual transmission is
obtained while at the same time making it possible to select the
thermal performance.
Energy control sheets for use on windows have heretofore been
commercially available in the marketplace. Typically this product
has consisted of an aluminum layer formed on plastic sheeting.
Aluminum in such applications has the capability of providing
substantially the same transmittance in the visual region as it
does in the solar region thereby limiting the solar reflectance as
a function of visual transmission. Typical aluminum films in the
marketplace are approximately 15 to 20 percent transmitting and
have a good thermal performance. There is a need for a new and
improved energy control sheet which has improved visual
transmission characteristics while retaining and improving the
thermal performance of the sheeting. In addition, aluminum coated
films have been found to be relatively non-durable and therefore
there is a need to provide a more durable energy control sheet.
In general, it is an object of the present invention to provide a
flexible selective energy control sheet and assembly thereof which
has improved visual transmission characteristics and good thermal
properties.
Another object of the invention is to provide an energy control
sheet and assembly thereof of the above character in which the
transmission which is obtained is substantially greater than that
which can be obtained with the use of aluminum and which has
thermal properties which is substantially as good as that of
aluminum.
Another object of the invention is to provide an energy control
sheet and assembly thereof of the above character which is
relatively durable.
Another object of the invention is to provide an energy control
sheet and assembly thereof the above character which is
aesthetically pleasing.
Another object of the invention is to provide an energy control
sheet and assembly using the same of the above character in various
colorations can be obtained.
Another object of the invention is to provide an energy control
sheet and assembly using the same of the above character in which
the energy control sheet can be prepared in a vacuum deposition
roll coater.
Another object of the invention is to provide an energy control
sheet and assembly using the same of the above character in which
the thermal control properties can be selected.
Another object of the invention is to provide a selective energy
control sheet and assembly using the same of the above character
which is particularly adapted for colder climates; for example, the
northerly latitudes in the northern hemisphere.
Another object of the invention is to provide an energy control
sheet and assembly thereof using the same of the above character
which is particularly adapted for warmer climates; for example, the
southern latitudes in the northern hemisphere.
Additional objects and features of the invention will appear from
the following description in which the preferred embodiments are
set forth in detail in conjunction with the accompanying
drawings.
FIG. 1 is a cross-sectional view of a flexible selective energy
control sheet incorporating the present invention utilizing
copper.
FIG. 2 is a cross-sectional view of an energy control sheet
incorporating the present invention utilizing silver.
FIG. 3 is a graph showing the performance of prior art unmounted
energy control sheets using aluminum.
FIG. 4 is a graph showing the performance of unmounted energy
control sheets of the present invention using copper.
FIG. 5 is a graph showing the performance of unmounted energy
control sheets of the present invention using silver.
FIG. 6 is a cross-sectional view of an assembly using a flexible
selective energy control sheet in which the sheet is mounted on
existing architectural glass for use in retrofit situations.
FIG. 7 is a cross-sectional view of a top coated form of energy
control sheet for use in the embodiment shown in FIG. 6.
FIG. 8 is a cross-sectional view of a laminate form of energy
control sheet for use in the embodiment of the invention shown in
FIG. 6.
FIG. 9 is a cross-sectional view of an assembly utilizing an energy
control sheet mounted on one surface of the two panes of glass in a
double pane construction producible by original equipment
manufacturers.
FIG. 10 is a cross-sectional view showing an assembly utilizing an
energy control sheet of the present invention in which the energy
control sheet is stretched between a double pane construction
producible by original equipment manufacturers.
In general, the flexible energy control sheet of the present
invention comprises a sheet of substantially transparent flexibile
polymer thin film plastic material. It has a thickness ranging from
12 micrometers to 200 micrometers and having first and second
surfaces. A substantially transparent substantially continuous
adhension promoting layer is adherent to the second surface of the
sheet. A substantially transparent metal layer is adherent to the
adhesion promoting layer. A protective layer is adherent to the
metal layer. The metal layer is selected to provide the desired
thermal characteristics while providing improved transmission. For
more northerly climates in the northern hemisphere, a silver-based
film is provided. For the more southerly climates in the northern
hemisphere, a copper-based film is provided.
In FIG. 1, there is shown a copper series (C series) or a copper
based energy control sheet. As shown therein, the energy control
sheet 16 consists of a layer 17 which serves as a substrate and has
a thickness ranging from two to 200 micrometers and with a typical
thickness ranging from 12 to 25 micrometers. The layer 17 should be
substantially transparent. It is formed of a flexible polymer thin
film plastic material of a suitable type such as polyethylene
terephthalate. Other possible substitute materials are
polypropylene, polyethylene, acrylic and other like polymer
substances. The layer 17 is provided with first and second surfaces
18 and 19. An adhesion promoting layer 21 is adherent to the second
surface 19 and serves as a bonding layer for a metal layer 22. The
adhesion promoting layer 21 should be substantially transparent and
should be sufficiently thick so as to provide a substantially
continuous layer for the metal layer 22. In addition, it must be
thin enough so as not to adversely interfere with the transmission
qualities of the optical properties of the resulting energy control
sheet 16. By way of example, the adhesive layer 21 could have a
thickness of approximately 20 Angstroms but could range from 10 to
100 Angstroms in thickness. One material found to be suitable for
this application is chromium in a thickness of approximately 20
Angstroms. Chromium was selected for this adhesion promoting layer
21 because it has excellent properties from the standpoint of its
durability at various temperature environments. Also it has
excellent adhesive qualities.
When the energy control sheet 16 is to be utilized in the southern
latitudes of the northern hemisphere, copper is used for the metal
layer. The copper layer 22 is applied to a thickness which is
consistent with the desired resultant transmission level as well as
the desired color. For example, the thickness of the copper layer
can range from 100 to 500 Angstroms with a typical copper layer
having a thickness of 150 Angstroms.
A protective layer 23 is adherent to the metal layer 22. The layer
23 serves to prevent oxidation and corrosion of the metal layer 22.
One metal found to be particularly suitable for this purpose was
chromium which can be deposited to a thickness of 10 to 200
Angstroms and at preferably a thickness of approximately 40
Angstroms for this layer 23.
In FIG. 2 there is shown an energy control sheet 26 which is of an
S-series or silver-based type. As shown in FIG. 2, such an energy
control sheet 26 consists of the layer 27 of a substantially
transparent flexible polymer thin film of plastic material of the
type hereinbefore described in conjunction with FIG. 2. It is
provided with front and rear surfaces 28 and 29. An adhesion
promoting layer 31 is adherent to the second surface 29 and serves
as a bonding layer for a metal layer 32. The adhesion promoting
layer 31 can be formed of suitable material such as zinc sulfide
and can have a suitable thickness ranging from 300 to 500 Angstroms
with a preferable thickness of approximately 400 Angstroms. The
metal layer 32 can be formed of a suitable material such as silver
having a thickness ranging from 60 to 200 Angstroms and preferably
a thickness of approximately 125 Angstroms. It should be pointed
out that the adhesion promoting layer 31 serves as a nucleating
layer as well as an optical layer for the silver layer 32. A
protective layer 33 is formed on the metal layer 32 and serves to
prevent oxidation of the silver layer 32 as well as to physically
protect the silver layer from abrasion. The protective layer 33 can
be formed of a suitable material such as zinc sulfide having a
thickness ranging from 300 to 500 Angstroms with a preferable
thickness being in the vicinity of 400 Angstroms. This layer is
also optically active.
As hereinafter can be seen, the C-series or copper-based energy
control sheets are particularly useful in what may be termed as
summer conditions or in other words would be particularly useful in
southern latitudes of the northern hemisphere whereas the S-series
or silver based designs are particularly useful for the northern
latitudes of the northern hemisphere where optimum solar energy
transmission and infrared rejection is the requirement.
The optical properties which are usually used as figures of merit
are the ratio of visually transmitted energy to solar isolation
(T.sub.vis /T.sub.solar) and the infrared emittance (.epsilon.f).
Other properties such as transmittance and reflectance measured
over the solar spectrum are used to calculate shading coefficient
(SC), U-factor and fraction of solar energy rejected or retained.
Typical spectra showing the performance of unmounted prior art
aluminum coatings is shown in FIG. 3. Typical spectra are shown in
FIG. 4 for unmounted energy control sheets of the present invention
using copper. Typical spectra are shown in FIG. 5 for unmounted
energy control sheets of the present invention using silver. Table
No. 1 set forth below shows the performance data for FIGS. 3, 4 and
5.
TABLE I ______________________________________ WINDOW FILM COATINGS
(UNMOUNTED) VISUAL SOLAR Design T.sub.v R.sub.f R.sub.b T.sub.s
R.sub.f R.sub.b T.sub.vis/T.sbsb.solar .epsilon..sub.f
______________________________________ C-20 .20 .50 .40 .12 .71 .65
1.65 .05 C-35 .34 .34 .19 .27 .50 .38 1.25 .10 C-50 .48 .27 .14 .39
.42 .32 1.23 .13 S-80 .82 .12 .14 .73 .20 .20 1.20 .10 AL-15 .17
.61 .60 .15 .64 .62 1.13 .33 AL-25 .27 .50 .48 .23 .53 .51 1.17 .40
AL-40 .43 .32 .30 .38 .35 .33 1.13 .50
______________________________________
In the above design, the C-20, C-35 and C-50 curves are for copper
based coatings whereas the S-80 curve is for a silver-based
coating. The AL-15, AL-25 and the AL-40 curves are for aluminum
based commercially available coatings that constitute prior
art.
The following optical and thermal definitions have been used in
connection with the graphs and FIGS. 3, 4 and 5 and in Table I
above.
Visual-ILL"B"
T.sub.v (%)=Percent Visual Transmittance The overall percent
transmittance over the visual wavelength range (0.4-0.7 .mu.m)
weighted against Illuminant "B" which approximates noonday sun
conditions.
R.sub.b (%)=The Overall Percent Reflectance, Back The overall
percent reflectance measured from the "uncoated" side over the
visual wavelength range (0.4-0.7 .mu.m) weighted against Illuminant
"B" which approximates noonday sun conditions.
R.sub.f (%)=The Overall Percent Reflectance, Front The overall
percent reflectance measured from the coated surface over the
visual wavelength (0.4-0.7 .mu.m) weighted against Illuminant "B"
which approximates noonday sun conditions.
Solar AM.sub.2
T.sub.s (%)=Percent Solar Transmittance The overall percent
transmittance over the wavelength range 0.25-2.2 m weighted against
Moon's AM.sub.2 solar curve.
R.sub.b (%)=Percent Reflectance, Back The overall percent
reflectance measured from the "uncoated" side over the wavelength
range 0.35-2.2.mu. weighted against Moon's AM.sub.2 solar
curve.
R.sub.f (%)=Percent Reflectance, Front The overall percent
reflectance measured from the coated surface over the wavelength
range 0.35-2.2 .mu.m weighted against Moon's AM.sub.2 solar
curve.
Thermal
T.sub.v /T.sub.s =Selectivity Ratio
The ratio of visual transmittance to solar transmittance being a
merit function of visibility through the film compared to solar
energy transmitted.
.epsilon.f=Emittance Front The hemispherical thermal emittance of
the film measured from the surface at approximately 30.degree.
C.
The curves shown in FIGS. 3, 4 and 5 are for transmittance and
reflectance. The solid lines are transmission curves and are
labeled T whereas the broken lines are reflectance curves and are
labeled R. A comparison of the curves shown in FIGS. 4 and 5 with
respect to the curves shown in FIG. 3 shows the dramatic
improvement in performance of the coatings of the present invention
over that which can be obtained with aluminum. The selectivity and
environmental performance are superior to the prior art aluminum
coated designs. Greatly improved visual transmittance can be
obtained with the same solar rejection with the energy control
sheets of the present invention in comparision to the prior art
aluminum based energy control sheets. The energy control sheets of
the present invention also give greater spectral selectivity
between the solar/visual and far infrared regions.
More specifically from FIG. 4, it can be seen that the transmission
peaks at approximately six-tenths of a micron and then gradually
drops off through the visible region with the transmittance
diminishing in the infrared region. This shows the desirable
transmission characteristic for the film and shows the selectivity
of the coating versus the prior art aluminum based coatings shown
in FIG. 3 which have no such peaking of transmittance in the
visible region. As shown in FIG. 3, in the prior art aluminum based
coatings, the transmission does not peak but has a value of at 0.6
microns associated with the identity for the coating as for example
the AL-40 coating has a transmittance of 40% at 0.6 microns. The
transmittance thereafter decreases slowly in the long infrared
region.
With respect to the silver based coatings shown in FIG. 5, it can
be seen that the transmission again peaks at approximately 0.6
microns and is substantially flat throughout the visible region and
thereafter decreases in the infrared region. Again this coating has
very desirable characteristics particularly when compared to the
prior art aluminum based coatings shown in FIG. 3.
The advantage of the coatings of the present invention is that they
have high solar transmission and are substantially colorless to the
eye. In addition, they have an added important characteristic which
is a consistent reflectance value below 20% which makes the coating
pleasing from a reflectance standpoint.
Products made in accordance with the present invention can also be
produced to have color. Thus for example the C-50 product shown in
FIG. 4 would have a neutral color by reflection. It also provides a
bronze tint in transmitted energy as well.
The designs which have hereinbefore been set forth with respect to
copper and silver as the base are of the type which can be produced
with vacuum roll coating equipment capable of simultaneous high
rate deposition of multi-layer coatings consisting of more than one
evaporant. The coatings for the energy control sheets of the
present invention have been specifically designed to selectively
enhance the transmission of semi-transparent metals by the
application of multi-layer thin film interference techniques.
In FIG. 6 there is shown an assembly 36 using an energy control
sheet. The assembly 36 is of a type which would be used in retrofit
applications. The assembly 36 consists of a conventional frame 37
in which there is mounted a pane 38 of glass of a suitable
thickness as for example one-eighth of an inch. The pane 38 of
glass is provided with an outside surface 39 and an inside surface
41. An energy control sheet is mounted on the inside surface 41.
The energy control sheet can be of the type shown in FIGS. 7 and
8.
The energy control sheet 42 as shown in FIG. 7 consists of a
plastic substrate 43 of the type hereinbefore described which
carries a C-series or S-Series type coating 44 formed of at least
three layers. This coating 44 is covered with a protective top coat
46 of a suitable material such as a polymeric or organic film or
coating of a thickness ranging from 5-50 microns. The top coat 46
serves as a protective top coat for the underlying three-layer
coating 44. The other side of the substrate 43 is provided with a
layer 47 of a conventional suitable mounting adhesive such as a
pressure sensitive adhesive. A conventional release liner 48
overlies the mounting adhesive 47 and serves to protect the
adhesive. When it is desired to place an energy control sheet 42 on
the inside surface of an existing pane of glass, the release liner
48 can be peeled away and the energy control sheet mounted on the
inside surface 41 of the pane 38. The mounting adhesive 47 will
hold the energy control sheet in place. The top coat 46 protects
the coating 44 so that the inside surface of the window can be
washed to keep it clean.
Another energy control sheet 51 of the type which can be utilized
in retrofit applications is shown in FIG. 8. It consists of a
plastic substrate 52 on which there is deposited a three layer
coating 53. A conventional laminating adhesive 54 is applied to the
coating 53. A cover 56 is carried by the adhesive layer 54. The
cover 56 can be of a suitable type such as of polypropylene or
polyethylene.
A conventional mounting adhesive layer 57 is provided on the other
side of the plastic substrate 52 and carries a conventional release
liner 58. The energy control sheet 51 shown in FIG. 8 can be
mounted on the inside surfaces of windows in the same manner as the
energy control sheet 42 shown in FIG. 7.
The energy control sheets of the present invention can be also
utilized by original equipment manufacturers to provide glazing
assemblies on which energy control sheets of the present invention
have been mounted. For example there is shown in FIG. 9 a double
pane assembly 61 which includes a frame 62. Two panes 63 and 64 of
glass of a suitable thickness such as one-eighth inch are mounted
in the frame 62 so that they are spaced apart in parallel positions
with a space 66 therebetween. An energy control sheet 67 of the
present invention is mounted between the panes of glass 63 and 64.
For example the energy control sheet 67 can be mounted on the
inside surface 68. As described with the energy control sheets 42
and 51 shown in FIGS. 7 and 8, the energy control sheets 67 can be
provided with a mounting adhesive (not shown) so that it is
supported by the inside surface 68 of the pane 64.
In FIG. 10 there is shown another assembly 71 of the type which
would be manufactured by an original equipment manufacturer which
includes a frame 72 which has mounted therein two spaced apart
parallel panes of glass 73 and 74 having a space 76 therebetween.
An energy control sheet 77 of the type utilized in the present
invention is disposed between the panes 73 and 74 and is stretched
within the frame 72 so that is positioned in the space 76
approximately equidistant from the inside surfaces of the panes 73
and 74. Spacers 78 have been provided adjacent the outer margin of
the energy control sheet 77 and the frame 72. In this way it can be
seen that the energy control sheet 77 is stretched between the
double pane glazing shown in FIG. 10. When this is the case, it is
unnecessary to provide the mouting adhesive on the rear side of the
plastic substrate for the energy control sheet 77.
In Table II set forth below are given the typical properties of
window film coatings mounted to one-eighth inch plate glass.
TABLE II ______________________________________ TYPICAL PROPERTIES
WINDOW FILM COATINGS (MOUNTED TO 1/8" PLATE GLASS) TOTAL PRO- SOLAR
T.sub.visual DUCT T.sub.visual T.sub.solar REJECTED U.sub.s U.sub.w
SC .epsilon..sub.f T.sub.solar
______________________________________ C-20 .22 .14 .71 .75 .80 .26
.25 1.57 C-35 .36 .27 .63 .74 .80 .39 .25 1.33 C-50 .49 .39 .52 .77
.83 .53 .30 1.26 S-80 .81 .65 .31 .69 .80 .78 .25 1.25 AL-15 .17
.14 .79 .77 .85 .22 .33 1.21 AL-25 .27 .22 .70 .82 .89 .32 .40 1.23
AL-40 .43 .35 .54 .89 .95 .49 .50 1.23
______________________________________
From the above it can be seen that a comparison is being made
between prior art aluminum based coatings and the copper and silver
based coatings of the present invention. Again it can be seen that
the visual transmission is substantially greater than that which is
obtainable by the prior art aluminum based coatings.
From the foregoing it can be seen that there has been provided an
energy control sheet and an assembly using the same in which is it
possible to obtain better selectivity in thermal optical
performance while at the same time obtaining higher visual
transmission. Also there have been provided energy control sheets
which have improved durability. When no coloring is desired, the
applications would be directed towards the silver based films
whereas when a bronze or subdued earthy color is desired, a copper
based film would be utilized. The energy control sheets are of a
type which can be utilized in retrofit situations or can be used in
original equipment manufacturers' products.
In addition the energy control sheet of the present invention can
be designed to accommodate different exposures on different sides
of a building.
* * * * *